Moving shards of reference tables was possible in at least one case:
```sql
select citus_disable_node('localhost', 9702);
create table r(x int);
select create_reference_table('r');
set citus.replicate_reference_tables_on_activate = off;
select citus_activate_node('localhost', 9702);
select citus_move_shard_placement(102008, 'localhost', 9701, 'localhost', 9702);
```
This would then remove the reference table shard on the source, causing
all kinds of issues. This fixes that by disallowing all shard moves
except for shards of distributed tables.
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
* When moving a shard to a new node ensure there is enough space
* Add WairForMiliseconds time utility
* Add more tests and increase readability
* Remove the retry loop and use a single udf for disk stats
* Address review
* address review
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>